Thread cutter for buttonhole sewing machines



NOV. 14, w w NNELL JR THREAD CUTTER FOR BUTTONHOLE SEWING MACHINES FiledMay 13, 1932 3 Sheets-Sheet 1 Fig. 1-.

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Nov. 14, 1933.

W. W. DUNNELL, JR

THREAD CUTTER FOR BUTTONHOLE SEWING MACHINES Filed May 13, 1932 5Sheets-Sheet 2 lnvenTor.

NOV. 14, 1933. w; w DUNNELL, JR 1,935,083

THREAD CUTTER FOR BUTTONHOLE SEWING MACHINES Filed May 15, 1952 5Sheets-Sheet 3 59 L- 24 InvenTor.

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Patented Nov. 14, 1933 THREAD CUTTER FOR BUTTONHOLE SEWING MACHINESWilliam W..Dunnc1l, J-r., Boston, Mass assignor to The Reece Button HoleMachine Company; Boston, Mass., a corporation of- Maine Application'May13, 1932,. Serial ,No. 611,077

3 Claims. (Cl. 112-252) This invention relates to buttonhole sewing mchines ofthat type in which the under thread mechanism is carried by aturret which is situatedbeneath the work and is rotatively mounted f rurningmovem nt.

The invention relates particularly to means for trimming the underthread and stay cord close to the work at the end of the .sewingoperation.

,One'of the objectsiof the invention is to provide a novel thread cutterwhich operates underneath the work between'the latter and the throatplate and which is given its thread-cutting movement by the reverserotation of the turret which occurs. after the sewing operation has beencompleted and before the machine comes to rest.

In order to give an understanding of the invention I have illustrated inthe drawings a selected embodiment thereof which will now be describedafter which the novel features will be pointed out.

in the appended claims.

,liig. 1 is aside view of a portion of a buttonhole sewing machineembodying the invention;

Fig, 2, is a top plan view of the work-holding means and the cutter forcutting the under thread and stay cord;

' 3 is a section on the line 33, Fig. 2;

Fig. 4 is a view .of the turret carrying the under thr d mec n m;

Fig. 5 is a top plan view of the turret illustrating the means foroperating the under thread cutting device;

Fig, 6 is a section on the line 66, Fig. 4;

Fig, 7 is a section on the line '77, Fig. 4;

.Fig, 8 is a fragmentary sectional view showing the manner in which theunder thread and stay cord are drawn around the edge of. the cuttingelement just before the cutter operates.

The buttonhole'sewing machine herein illustrated has the usualwork-holding means which is mounted on the bed plate 1 and the'usualstitchfo ming mechanism which is carried by a stitch frame indicatedgenerally at 2. The stitch frame and the .bed plate have a movementrelative to each other during the sewing on the buttonhole and also afurther relative movement to carry the parts from stitching tobuttonhole cutting position as usual in buttonhole sewing machines ofthis type.

The work-holding means comprises work clamps 3 by which the work 4 isclamped against the mats 5 which are carried by the clamp plates 6, thelatter being removably mounted on the bed plate 1 as usual.

The stitch-forming mechanism comprises the usual needle 7 carried by aneedle bar 8 which is mounted for reciprocation in the stitch frame 2,

and also under thread mechanism carried by the turret 9 which isrot'atively mounted in the portion 10 of the stitch frame on theopposite side of the work from the needle. i

The turret 9 carries the usual throat plate or button 11 which isprovided with the sewing opening 12 through which the needle '7operates.

The under thread mechanism is of that known type which comprises loopersand loop Spreaders (not shown) which are carried by the turret 9 and thelooper mechanism is actuated through the medium of'two co-axial spindles18 and 24 which are mounted for vertical reciprocation in the turret,the spindle 18 being connected through a link 17 to an oscillating blockwhich carries the looper, and the spindle 24 being connected by a link23 to the wedge for actuating the loop Spreaders. These spindles areconnected at their lower ends to levers 19 and 25 which are pivota'll-ymounted on the portion 10 of the stitch frame as indicated at 20 and 25and said levers 19 and 2 5 are connected by links 21 and 27 toappropriate cam-actuated levers (not shown) such as are usually employedin buttonhole sewing machines of this type for actuating the loopermechanism. I

In the operation of the buttonhole sewing ma-' chine the stitchframe 2and the work-holding means have a relative feeding movement during thesewing of the buttonhole and when the buttonhole has been completed andthe stitch-form ing mechanism has come to rest with the needle retractedas shown in Fig. 1, said stitch frame and work-holding means have afurther relative movement to carry the parts from stitching tobuttonhole cutting position. The full lines Fig.

1 illustrate the position of the parts at the completion of thebuttonhole sewing, andthe dotted lines indicate the position of thestitch frame when shifted into huttonhole cutting position.

During the sewing on the buttonhole the under thread 28 is led to thework from the threaded looper through the sewing opening 12" of thethroat plate 11 and the stay cord 29 is also led to the work throughsaid sewing opening 12; When the parts are shifted from stitching tobuttonhole cutting position the stitch-forming mechanism movesforwardly, or. to the right Fig. 1 7 relative to the work-holding meansand to the work held thereby, and during this forward move- .ment'alength of under thread 28 and stay cord 29 will be drawn out through thesewing opening 12 as shown in Fig. 5 so that when the parts reachbuttonhole-cutting position there will be cord 29 extending from thestitched buttonhole 30 to the throat plate 11 and lying on the oppo siteside of the work from the needle. Since Fig. 8 is a view looking at theturret from the side opposite to that seen in Fig. 1, the movement ofthe turret and throat from stitching to buttonhole cutting position willbe toward the left in said Fig. 8.

The present invention relates to the thread cutter and the means foractuating it by which the under thread 28 and stay cord 29 are cut closeto the work.

The thread cutter is similar to that shown in the co-pending Pikulapplication Serial No. 525,092, filed March 25, 1931. This cutterconsists of a swinging cutter element 79 fast to a stud 80 mounted forturning movement in one of the clamp plates 6. This cutter has anarcuate work-positioning edge 81 and a thread-engaging finger 82 whichis provided with a cutting edge 83. v 1

During the sewing on the buttonhole the cutter "/9 is positioned asshown in Fig. 2 with the work-positioning edge 81 crossing the sewingopening, it being held in this position by a spring 54 so that when thestitch frame and workholding means have their relative movement afterthe stitching of the buttonhole is completed to carry the parts fromstitching to button-holecutting position, the length of under thread andstay cord which have been pulled through the sewing opening 12 of thethroat plate will be drawn tightly around the work-positioning edge 7 81and the latter will serve to hold the work properly positioned. It willbe understood that the work clamps are opened before the cutter isactuated to cut the under thread and stay cord.

Means are herein provided for giving the thread cutter '79itsthread-cutting movement directly by the reverse turning movement ofthe turret which occurs after the completion of the sewing of thebuttonhole. I

For this purpose the stud 80 is provided with an arm 55 carrying a roll56 and the turret 9 is provided with an upstanding arm '70 which carriesat its upper end a cam member 57 adapted to engage the roll 56 duringthe reverse turning movement of the turret in the direction of the arrowFig. 5 thereby to turn the stud 80 and thus give the trimming knife 79its operative threadcutting movement. This is shown in Figs. 2

v and 5.

tion.

The dotted lines in Fig. 2 indicate the position of the turret and thecam member 57 relative to the roll 56 after the stitching on thebuttonhole has been completed and the parts have been moved fromstitching to buttonhole-cutting posi- In this position the cam member5'? is closely adjacent the roll 56. When the turret is given itsreverse turning movement in the direction of the arrow Fig. 5 theengagement of the cam'member 57 with the roll 56 will turn the pivotallyconnected. The turret is shown as hava length both of the under thread28 and stay stud 80 thereby giving the knife '79 its threadcuttingmovement as shown by dotted lines Fig. 5.

In the operation of the under thread mechanism it is desirable that thespindles l8 and 24 should be held from turning movement as they arereciprocated so that the links 1'? and 23 may always be operated in thecorrect position.

The spindles 18 and 24 have crossheads 59 and 60 fast thereto to whichthe links 17 and 23 are ing a vertically-extending guiding fin 61secured thereto and the crosshead 59 is provided with a forked extension62 which embraces said fin. The crosshead 60 is similarly provided witha forked extension 63 which also embraces the fin. The same fin thusguides both crossheads in their vertical movement and prevents anyturning movementof the spindles and thus any tendency of the parts tobind.

I claim:

1. In a button hole sewing machine, the combination with work-holdingmeans, of a stitch frame, stitch-forming mechanism carried thereby andincluding under thread mechanism, a turret rotatably carried by saidframe and on which the under thread mechanism is mounted, athread-cutting member pivotally carried bythe work-holding means, saidturret having a reverse rotative movement at the completion of thebuttonhole, and means to give the cutter member its operative movementby such reverse movement ofv the turret.

2. In a buttonhole sewing machine,- the combination with work-holdingmeans, of a stitch frame, stitch-forming mechanism carried thereby andincluding under thread mechanism, a turret rotatably carried by saidframe and on which the under thread mechanism is mounted, athreadcutting member pivotally carried by the workholding means, saidturret having a reverse rota- 115 tive movement at the completion ,ofthe buttonhole, an arm rigid with the cutter and a cam carried by theturret adapted to engage said arm duringsuch reverse rota/tive movementthereby to actuate the cutter.

3. In a buttonhole-sewing machine, the combination with work-holdingmeans including clamp plates on which the work rests, means to clamp thework against saidplates, of 'a stitch frame, stitch-forming mechanismcarried thereby 125 and including under thread mechanism, a turret,rotatively carried by said stitch frame and on which the under threadmechanism is mounted, said turret having a reverse rotary movementat thecompletion of the buttonhole, a thread-cut- 130 ting member for trimmingthe under thread and stay cord operating between the work and the. clampplates, an arm rigidwith the cutting memher and situated beneath theclamp plates, and a cam member on the turret for engaging the arm 135thereby to give the cutter its operative movement as the turret has itsreverse rotative movement.

WILLIAM W. DUNNELL. JR.

